Common to most operating BWR's, the core spray cooling water is delivered to the reactor core region by piping 10 internal to the reactor vessel. A portion of this internal piping is a horizontal segment 12, which is formed to follow the radius of curvature of the reactor vessel wall. The proximal end 14 of the horizontal piping 10 is connected to a T-Box 16 at the core spray nozzle penetration. The piping configuration near the vessel T-Box 16 is shown in FIG. 1.
The core spray piping systems in operating BWR's are of welded construction. The weld connecting the horizontal piping segment 12 to the T-Box 16 is designated as the P3 weld. The distal end of the horizontal core spray line 10 is welded to a short radius elbow. This weld joining the distal end of the core spray line 10 to the short radius elbow is designated as the P4a weld. In at least one BWR, there is another weld in the core spray line 10 in close proximity to the T-Box 16. This weld is designated as the P3a weld.
The welds in core spray system piping are susceptible to Intergranular Stress Corrosion Cracking (IGSCC). In the event that cracking should occur in the P3a weld, the structural integrity of the core spray line 10, which delivers cooling water to the reactor core, would be lost. A preemptive repair would be to design, fabricate, and install a hardware device that would prevent separation of the P3a weld in the event that circumferential through-wall cracking should occur at this weld location in the core spray line.